Which hormone is released by the stomach and pancreas and increases the sensation of hunger?

Ghrelin is a hormone produced primarily in the stomach, with some release also occurring from the pancreas. Its primary function is to stimulate appetite, which increases the sensation of hunger. When the stomach is empty, ghrelin is released into the bloodstream, signaling to the brain that the body needs food. This hormone acts on the hypothalamus, the brain region responsible for regulating hunger and energy balance.

In contrast, other hormones listed serve distinct functions. Leptin, for example, is produced by adipose (fat) tissue and plays a role in suppressing appetite, essentially signaling to the brain that there is enough energy stored and that it's time to reduce food intake. Cortisol, a hormone released from the adrenal glands in response to stress, can influence appetite and metabolism but does not directly stimulate hunger in the same way as ghrelin. Insulin, produced by the pancreas, regulates glucose levels in the blood and also affects metabolism but does not have a primary role in stimulating hunger.

Therefore, ghrelin is the correct answer as it directly increases the sensation of hunger, aligning with its functions in the body's energy regulation system.